Inventories (Tables)

3 Months Ended

Mar. 31, 2018

Inventory Disclosure [Abstract]

Schedule of Inventories

Inventories are summarized as follows:

	MARCH 31 2018		DECEMBER 31 2017
Coal	$	12,371	$	13,416
Mining supplies	17,744		16,599
Total inventories	$	30,115	$	30,015